Seasonal variation in the barrier layer of the Banda Sea

The Banda Sea is crucial to the circulation of the world's oceans and atmosphere due to its location within the equatorial regions of the Indonesian Maritime Continent. It links the Pacific and Indian Oceans' circulation via the Indonesian Throughflow and contributes to driving atmospheric conditions via heat and moisture fluxes. Strong salinity-stratified barrier layers have the potential to play a significant role in air-sea interaction by separating the base of the mixed layer from the top of the thermocline and reducing the exchange of surface heat and momentum with the ocean's subsurface. In this study, we present the seasonal variability of barrier layer thickness (BLT) and its formation mechanism in the Banda Sea using the eddy-resolving ocean reanalysis Bluelink version 2020 (BRAN2020) for 1993 to 2021 and air-sea flux data. The findings show that the BLT is a persistent feature in the Banda Sea with a strong seasonal cycle. The BLT maxima appear in the southeast monsoon season period from May to July and the minima in the pre-northwest monsoon season from October-November. The spatial distribution of BLT is zonally oriented along the sea surface salinity (SSS) front from the west to the east of the Banda Sea. We suggest that the horizontal advection of low salinity water from the Java Sea and precipitation contributes to the formation of BLT formation and variability in the Banda Sea.